I have a web based product developed in java, now my requirement is to put a spy kind of thing, so that i can find out which module of the product is using very much, without putting performance overhead. I want to records information somewhere after visting each module by end users without thier information. Please suggest.
The Java API has a logging package.
Although myself I would use log4j.
Once you pick one then you add logging statements throughout your application with appropriate data logged.
You can then create a tool that parses the logs and correlates the data for you. There are are 3rd party products that will parse logs to.